Cancer and its associated therapies are some of the biggest health concerns in the world. The two main forms of treatment for cancer are chemotherapy and radiotherapy.
Chemotherapy, in combination with or as an alternative to surgery, is the method of choice in most cases for controlling or helping patients struck by carcinomas. Chemotherapy is defined as the use of chemical substances to treat disease and, in the sense of this invention, refers primarily to the use of cytotoxic or cytostatic drugs, called chemotherapeutic drugs, to treat cancer. In general it is a systemic treatment. Chemotherapy in cancer treatment consists of a personalized combination of potent chemotherapy drugs, designed to slow rapid cancer tumor growth, shrink tumors, kill cancer cells, and prevent the spread of cancer. The chemotherapeutic drugs prevent cells from replicating in the typical, out-of-control manner in which cancer cells divide.
Radiotherapy (or radiation therapy), on the other hand, involves the targeted use of ionizing radiation in cancer treatment. Radiotherapy is also commonly used in combination with other methods such as chemotherapy.
Anti-cancer therapy, such as the use of radiation or the administration of chemotherapeutic agents, is associated with Adverse Events including radio and chemotherapy-associated toxicities. Such toxicities and/or side-effects can materially offset or limit the potential benefits to the patient undergoing treatment, for example, resulting in treatment delays, treatment interruptions, dose modifications, dose schedule modifications, or even complete cessation of treatment. Thus, in addition to their adverse pharmacological affects, the development of said toxicities can limit or curtail the effectiveness of the primary treatment of the patient's cancer or preclude it all together. Cessation, interruption, or delays in patient treatment, or reducing the dosage of chemotherapeutic therapy or the fractions of radiotherapy, for example, may be detrimental to a subject's chances of long-term survival or control of the cancer, since such alterations in the treatment can allow the progression of cancer within the subject.
Emesis is a well-known and frequent side-effect of cancer chemotherapeutic agents, such as cisplatin, as well as of radiotherapy. It causes serious problems, and in some patients emesis is so severe that therapy must be discontinued. Anti-emetic agents are therefore often administered in order to alleviate this side-effect of the cancer chemotherapeutic agent or radiation. The anti-emetic agents employed are usually benzamide derivatives, such as metoclopramide, which have dopamine antagonist activity. In view of their dopamine antagonist activity benzamide derivatives such as metoclopramide themselves exhibit serious and undesirable side-effects, such as extra-pyramidal effects, i.e. tardive dyskinesia, acute dystonia, akathisia and tremor. Other anti-emetic drugs include 5-HT3 antagonists, e.g., ondansetron; corticosteroids, e.g., dexamethasone; and NKI antagonists, e.g., aprepitant. These treatments fail to adequately address the needs of the patient. Serious side effects that may occur due to the use of antiemetics include fever, hearing loss, extreme nausea, constipation, ringing ears, severe stomach pain, severe vomiting, heartburn and unusual weight gain. Allergic reaction marked by swelling of the face or throat may also occur as a result of using antiemetics. Other less-serious side effects that may occur as a result of using antiemetics include darkening of the stool or tongue, drowsiness, dry mouth, mild nausea, stomach pain and headache.
Several reports on the drawbacks of anti-emetic drugs have been published. Although there is no consensus on the severity of said drawbacks such as the side effects, it is commonly agreed that they must be mitigated. In this sense, J. Raynov [Archive of Oncology 2001; 9(3):151-3] studies the side effects and reactions caused by antiemetics in patients under chemotherapy treatment and concludes that the most common side effects (extrapyramidal reactions, headache, constipation . . . ) are usually mild and controlled by symptomatic treatment, but they have to be identified by the medical staff and the patients.
The efficacy and adverse effects of known antiemetics (droperidol, ondasetron, hyoscine TTS, tropisetron, metoclopramide, propofol, promethazine) during Patient-Controlled Analgesia Therapy, a highly emetogenic treatment, has also been evaluated [Martin R. Tramèr et al. (Anaesth Analg 1999; 88: 1354-61)]. Although the results must be confirmed and completed, the authors state regarding droperidol that the risk of adverse effects is dose-dependent. Likewise, 5-HT3 receptor antagonists (ondasetron, tropisetron) shown no evidence of any antinausea effect.
On another front, it is known in the art that neuropathic pain, allodynia, hyperalgesia, and especially, peripheral neuropathy, develop in a considerable number of cases as a result of chemotherapy. These are very specific symptoms arising from the neurotoxicity of the chemotherapeutic drug. The treatment of these symptoms is crucial for preserving the quality of life of the afflicted patients (Mielke et al., Eur. J. Cancer, 2006, 42(1), 24-30; Park et al., Curr. Med. Chem., 2008, 15(29), 3081-94; Argyriou et al., Blood, 2008, 112(5), 1593-9). Unfortunately, an effective treatment for chemotherapy-induced peripheral neuropathy has yet to be found (Wolf et al., Eur. J. Cancer, 2008, 44(11), 1507-15). WO 2009/103487 and co-pending application EP 09382144.5 relates to the use of sigma receptor ligands in the prevention or treatment of pain resulting from chemotherapy.
In view of the above, an effective treatment for emesis that minimizes or eliminates one or more of this side effect of currently available cancer therapies is highly desirable. Therefore, there is an urgent need to provide a new form of treatment and/or prevention for the emesis associated to chemotherapy or radiotherapy. Preferably, the therapy should also be useful for treating and/or preventing other conditions developed as result of chemotherapy or radiotherapy, such as pain induced by chemo- or radiotherapy.